全文获取类型
收费全文 | 18270篇 |
免费 | 1318篇 |
国内免费 | 405篇 |
专业分类
电工技术 | 701篇 |
综合类 | 486篇 |
化学工业 | 3181篇 |
金属工艺 | 591篇 |
机械仪表 | 667篇 |
建筑科学 | 900篇 |
矿业工程 | 166篇 |
能源动力 | 472篇 |
轻工业 | 1783篇 |
水利工程 | 246篇 |
石油天然气 | 268篇 |
武器工业 | 75篇 |
无线电 | 2087篇 |
一般工业技术 | 2647篇 |
冶金工业 | 3048篇 |
原子能技术 | 188篇 |
自动化技术 | 2487篇 |
出版年
2024年 | 72篇 |
2023年 | 251篇 |
2022年 | 484篇 |
2021年 | 746篇 |
2020年 | 555篇 |
2019年 | 480篇 |
2018年 | 619篇 |
2017年 | 591篇 |
2016年 | 608篇 |
2015年 | 639篇 |
2014年 | 779篇 |
2013年 | 1122篇 |
2012年 | 1080篇 |
2011年 | 1183篇 |
2010年 | 887篇 |
2009年 | 801篇 |
2008年 | 864篇 |
2007年 | 730篇 |
2006年 | 616篇 |
2005年 | 491篇 |
2004年 | 419篇 |
2003年 | 370篇 |
2002年 | 380篇 |
2001年 | 305篇 |
2000年 | 285篇 |
1999年 | 288篇 |
1998年 | 1033篇 |
1997年 | 620篇 |
1996年 | 436篇 |
1995年 | 251篇 |
1994年 | 250篇 |
1993年 | 240篇 |
1992年 | 102篇 |
1991年 | 116篇 |
1990年 | 89篇 |
1989年 | 112篇 |
1988年 | 74篇 |
1987年 | 68篇 |
1986年 | 62篇 |
1985年 | 82篇 |
1984年 | 63篇 |
1983年 | 63篇 |
1982年 | 75篇 |
1981年 | 66篇 |
1980年 | 49篇 |
1979年 | 42篇 |
1978年 | 42篇 |
1977年 | 85篇 |
1976年 | 108篇 |
1975年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
51.
52.
53.
This paper describes the application of an expert system for the evaluation of the short-term thermal rating and temperature rise of overhead conductors. The expert system has been developed using a database and Leonardo expert system shell which is gaining popularity among commercial tools for developing expert system applications. The expert system has been found to compare well when evaluated against site tests. A practical application is given to demonstrate the usefulness of the expert system developed 相似文献
54.
B Amy de la Bretèque 《Canadian Metallurgical Quarterly》1995,116(4):271-272
The adolescent's breaking of the voice is the result of the substitution of the chest voice (or heavy mechanism) for the head voice (or light mechanism). In cases of late breaking, the voice is abnormally high-pitched and feeble, often with a distorted timbre, while the larynx is normal and pubescent. Such people are generally not fully aware of their voices' real nature. Therapy classically resorts to laryngeal manipulations, of which a new technique is put forward. Another therapeutic approach is based, on the one hand, on critical listening compared with a control male voice, thus enabling the subject to become aware of his own voice, and, on the other hand, on high intensity work which helps passing from head to chest voice. 相似文献
55.
Activation of macrophages by T cells is considered an initiating event in glomerular crescent formation. Since interferon-gamma (INF gamma) is a key mediator in T-cell-mediated activation of macrophages, we decided to test its role in a model of crescentic glomerulonephritis. An anti-glomerular basement membrane (GBM) serum was injected intravenously in presensitized wild-type or IFN gamma receptor deficient (IFN gamma(R)-/-) mice. Glomerulonephritis with glomerular crescents and tubulointerstitial inflammation developed in both strains, even though most evaluated morphological parameters and proteinuria indicated a less severe pathology in the mutant mice compared to the wild type. Thus, IFN gamma is not essential either for glomerular crescent formation or for tubulointerstitial involvement in anti-GBM glomerulonephritis in mice. In conclusion, the role of macrophages in this model might have been overestimated, or other cytokines may compensate for deficient IFN gamma signaling in the activation of macrophages. 相似文献
56.
The network interconnection and its regulation consist in solving the following dilemma: increase competition and preserve the universal service through access charges, which symbolizes today institutional organization within the telecommunication industry. This paper presents some of the economic and social factors that drive the interconnection policies namely ona (open network architecture) in the United States, or onp (open network provision) in Europe. In the first section, we list some social and economical issues related to open network policies. In the second section, we study the different answers brought up by the regulator through alternative interconnection price formulas. In conclusion, we discuss the stakes and risks of interconnection, while the technological evolution of network introduces intelligent software in switching équipement and implements the tremendous abilities of the digital broadband networks. 相似文献
57.
Extending the Kernighan/Lin Heuristic for Hardware and Software Functional Partitioning 总被引:5,自引:0,他引:5
The Kernighan/Lin graph partitioning heuristic, also known as min-cut or group migration, has been extended over several decades very successfully for circuit partitioning. Those extensions customized the heuristic and its associated data structure to rapidly compute the minimum-cut metric central to circuit partitioning; as such, those extensions are not directly applicable to other problems. In this paper, we extend the heuristic for functional partitioning, which in turn can solve the much investigated codesign problem of partitioning a system's coarse-grained functions among hardware and software components. The key extension customizes the heuristic and data structure to rapidly compute execution-time and communication metrics, crucial to hardware and software partitioning, and leads to near-linear time-complexity and excellent resulting quality. Another extension uses a new criteria for terminating the heuristic, eliminating time-consuming and unnecessary fine-tuning of a partition. Our experiments demonstrate extremely fast execution times (just a few seconds) with results matched only by the slower simulated annealing heuristic, meaning that the extended Kernighan/Lin heuristic will likely prove hard to beat for hardware and software functional partitioning. 相似文献
58.
A method of posterior mitral annulus remodeling is presented. The posterior annulus is divided into three segments, each segment encircled by a suture that is passed in a tourniquet. Coaptation of the leaflets can be achieved by tightening the tourniquets while the ventricle is being filled. This technique is simple and quick, avoids the use of foreign material, and requires less expertise and judgment than traditional annuloplasties. 相似文献
59.
N Fondevila V O'Donnell S Duffy E León E Smitsaart AA Schudel 《Canadian Metallurgical Quarterly》1997,16(3):784-792
A sero-epidemiological survey was conducted in two districts in Argentina between 1993 and 1995, to provide additional information on the epidemiology of foot and mouth disease (FMD) in Argentina and to assess the level of immunity in cattle populations, and the circulation of FMD virus. As part of the final stage of this survey, a comparison was made of the results obtained by the enzyme-linked immunosorbent assay (ELISA) and agar gel immunodiffusion techniques. Levels of population immunity against the four types of virus included in the vaccine increased progressively during the period of the survey until, in 1995, at the end of the vaccination period, the percentage of animals possessing adequate levels of protection was approximately 77% in yearlings, and more than 94% in cattle over one year old. During the three-year study, there was a clear tendency for viral activity to diminish, until in 1995 when between 3% and 0.6% were positive to the agar gel immunodiffusion test for the antigen associated with viral infection. By contrast, the ELISA detected antibody in about five times as many animals. The authors show how the increase in the level of population immunity was accompanied by a fall in viral activity. 相似文献
60.